Formation of the circuit in hydrodynamic torque converters



May 28, 1968 l A. LYSHOLM 3,335,061

FORMATION OF THE CIRCUIT IN HYDRODYNAMIC TORQUE CONVERTERS Filed June20, 1966 2 Sheets-Sheet 1 L V E 2 1 23- v A 1-3- )18 1 28 -19 L Qzzmvrozz. i\\\\\\\\ 1 BY; W

y 28, 1958 A. LYSHOLM 3,385,061

FORMATION OF THE CIRCUIT IN HYDRODYNAMIC TORQUE CONVERTERS Filed June20, 1966 2 Sheets-Sheet 2 VFIG.Z.

fix 1g VEN TOR. Mm, rauv United States Patent 3,385,061 FORMATION OF THECIRCUIT IN HYDRO- DYNAMIC TORQUE CONVERTERS Alf Lysholm, Karlaplan 11,Stockholm, Sweden Filed June 20, 1966, Ser. No. 558,799 Claims priority,application Sweden, June 28, 1965, 8,483/65 5 Claims. (Cl. 60-54)ABSTRACT OF THE DISCLOSURE Flow losses in a hydrodynamic torqueconverter are reduced by providing an improved configuration for aninner bend of a torus-shaped working chamber in the converter. Thethrough-flow area of the inner bend of a working chamber circuit isformed with a successively increasing restriction of at least 5% inorder to obtain a maximum restriction ahead of the impeller entrance ata certain radial section of the inner bend. Also, a sealing slot may beformed between a portion of a curved reaction blade ring and an adjacentimpeller blade ring to reduce flow separation by a Coanda effectproduced by leaking current through the sealing slot.

This invention relates to hydrodynamic torque converters having a torichydraulic working chamber in which impeller blades, turbine blades andreactor blades are arranged in a conventional manner, and the object ofthe invention is to reduce the flow losses by suitable formation of theradially inner bend of the working chamber.

In torque converters of this kind the rotatably mounted impellerreceives mechanical energy from an engine. In the working chamber thisenergy is partly converted into hydraulic energy due to the fact thatthe impeller blades impart an increased head to a hydraulic fluidconfined in the working chamber at superatmospheric pressure and due tothe fact that the hydraulic fluid is positively circulated in theworking chamber.

As a result the fluid is caused to flow through the turbine and impartsrotation to a turbine disc that carries the turbine blades. The turbinedisc is connected to a turbine shaft which may be the output shaft ofthe transmission.

The reactor or stator blades are either secured to a single stationarymember or divided into a group secured to a stationary member and agroup secured to a freely rotatable member. In both cases the stationaryreactor stabilizes the flow at high speed ratios.

In the above named type of torque converters a great amount ofcirculating liquid is of high importance and, therefore endeavours aremade to reduce the flow losses by suitable choice of the number ofblades in the members of the converter and by suitable design of theprotiles and angles of the blades and of the toric circuit.

For this purpose it is known to reduce the blade losses and shock lossesof the torque converter by forming both the turbine blades and theliquid-guiding reactor blades with different thicknesses at the entranceand exit edges and by the provision of favourable aspect ratios andpitch ratios, the aspect ratio being the ratio of the length to thewidth of the blade and the pitch ratio being the ratio of the bladepitch to the width of the blade.

In hydrodynamic torque converters characterized by a high stall torqueat a flat efiiciency curve within the possible speed range it is commonpractice to provide no blades in the radially outer and radially innerbend of the toric circuit so that the bends are in the form of passagesfor free flow of the hydraulic fluid. The cross-section of the flow insuch bends is defined by an inner core ring carried by the reactor orturbine and by the internal toric surface of the working chamber. Inprior-art constructions this cross-section is substantially throughoutconstant.

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Yet it is known to devise the bends in consideration such that they arefirst diverging from the entrance and then converging toward the exitthereof with the maximum cross-sectional area located midway between theentrance and exit. Further, theories have been presented claiming thatthe formation of the radially inner bend of the working chamber relativeto the outer bend is of minor importance because of the fact that thevelocity components of the flow through the inner bend, f.i. between thereactor exit and the impeller entrance, are counteracting each other soas to reduce the risk of flow separation. There is no doubt that suchreasoning is justified, but recent flow measurements have proved thatwith conventional cross-sectional areas of the inner bend of the circuita considerable flow separation nevertheless occurs especially along theinner radius at the impeller entrance with the result of flow losses ofthe order of 2% The present invention has for its object to reduce theabove mentioned flow losses by a proper form of the torus-shaped workingchamber of a hydrodynamic torque converter. In said working chamber animpeller blade ring is provided for rotation and for radial outward flowof the hydraulic working fluid. One or more turbine blade rings are alsoprovided in said working chamber and one or more reactor blade rings arealternatively provided for radial outward flow and/ or radial inwardflow, said blade rings forming radially inwardly and outwardly directedflow channels, which are connected to an outer and an inner bladelessbend to form a closed transverse circuit of the working chamber. Theouter boundary surface of this circuit is obtained by a combinedcooperation between the internal surface of a casing surrounding theworking chamber and by the hubs of the blade rings. The inner boundarysurface of the circuit is formed by the respective inner rings of theblade rings which are provided to fit into and to each other to form acentral core ring in the working chamber. The hydrodynamic torqueconverter of the kind referred to above is according to theinvention'substantially characterized in that the through-flow area ofthe inner bend of the circuit seen in the direction of flow is formedwith a successively increasing restriction of at least 5% in order toobtain the maximum restriction ahead of the impeller entrance in across-sectional radial relative to the boundary surface of the impellerentrance and taken through the edge of the core ring where the innerperipheral guidance for the inner ring of the reactor blade ringterminates. The starting place of said restriction lies within the rangeof two thirds of the length of flow between the entrance and the exit ofsaid bend. The through-flow area along the length of flow between theentrance of the bend and the starting place of the restriction ispreferably constant.

As a result of the form of the working chamber according to theinvention the speed of the working fluid is increased upon the flowthrough the nozzle-like restriction of the inner bend which has shownadvantageous in order to prevent a flow separation and which has furtherresulted in that torque converters having a working chamber formedaccording to the invention have a higher efficiency and a wider workingrange than torque converters having a conventional form of the workingchamber.

The invention may be applied to any kind of working chamber of ahydrodynamic torque converter and to this end the invention is furthercharacterized in that in such cases where the radial inward flow channelwhich is by less than 8% greater than the through-flow area of theimpeller entrance, the through-flow area of the entrance downstream themaximum restriction seen in the flow direction and immediately ahead ofthe impeller entrance is formed with a small shoulder-like wideningwhich causes a flow separation and effects a Carnot shock and as aresult thereof a moderate vortex. This vortex reestablishes a thinboundary layer at the impeller entrance and improves the flow in theimpeller blade ring. Due to the small widening the losses due to theCarnot shock will be small (about 0.1%

The hydrodynamic torque converter according to the invention is furthercharacterized in that a sealing slot may be provided between theradially inner edge of the inner ring of the impeller blade ring and theradially inner surface of a recess formed in the inner ring of thereactor blade ring, said sealing slot being so shaped that it will bepossible to utilize the leaking current in order to obtain a Coandaeffect, i.e. a reduction of the boundary layer so that the boundarylayer along the inner sides of the impeller blades will become thinnerand flow separation will be counter-acted.

A hydrodynamic torque converter according to the invention will bedescribed more in detail with reference to the annexed drawings showingsuitable embodiments for a single-stage, two phase and double rotationtype, respectively, FIGS. 1 to 3 illustrating axial longitudinalsectional views of one-half of the various working chamber of therespective torque converters.

Referring to the embodiment of the Single stage converter illustrated inFIG. 1 more than half of the external boundary of the working chamber isdefined by the internal surface of a two part casing 10, 1b which in amanner not shown is secured to the support of the torque converter. Theremaining external boundary surface of the working chamber is formed bythe hub of an impeller 2 and by an outer lateral ring 3b of a set ofturbine blades 3a.

Secured to the half 1a of the casing is a set of reactor blades 4a theinner ends of which are connected to and, carry a core ring 5. On theside remote from the reactor blades 4a the core ring has a recess 5a inwhich both an inner lateral ring 3c for the turbine blades 3a and aninner ring 2c for the blades 2a of the impeller 2 are rotatably disposedand smoothly merge into the external surface of the core ring 5.

The impeller 2 is by means of splines or the like secured on a tubularshaft 6 which by means of a ball bearing 7 in the half 1a of the casingand by means of a journal bearing 8 or the like in a turbine disc 3 isrotatably mounted for transmitting mechanical energy from an engine, notshown, to the torque converter.

The impeller blades 2a impart circulating motion to a hydraulic fluidwhich at superatmospheric pressure is confined in the working chamber.The liquid flows through the set of turbine blades 3a so as to impartrotation to the turbine wheel 3. This turbine wheel 3 is formed with aturbine shaft 3d which is rotatably mounted in a ball bearing 9 in thehalf 1b of the casing and is the output shaft of the transmission.

In a working chamber formed as described above the joining externalboundary surfaces 1b, 2b, 3b and the core ring 5 together with thejoining inner rings 2c, 30 for the blades 2a, 3a define a circuit forthe hydraulic fluid, said circuit comprising a radial outward flowpassage 10 and a corresponding inward flow passage 11 communicating witheach other through an outer and an inner bladeless bend 12 and 13,respectively.

As mentioned above, the impeller blades 2a and the turbine blades 3a arerotatably disposed in the outward flow passage 10, whereas the stator orreactor blades 4a which deflect the liquid in a certain direction arestationarily mounted in the inward flow passage 11. The location of theturbine blades 3a radially outwardly of, and in immediate successionafter the impeller blades 2a as viewed in the direction of flow, renderspossible effective utilization of the various velocity components fromthe impeller exit for torque conversion.

In the embodiment illustrated in FIG. 1 the cross-sectional area of theinward flow passage 11 of the circuit is slightly greater than thecross-sectional area of the outward flow passage 10, and thecross-sectional area of the outer connecting bend 12 is substantiallyconstant. Tests have proved, however, that it is possible, in order toreduce the external diameter of the casing 1a, 1b to reduce thecross-sectional area by about 10% midway of the bend 12 without theoccurence of additional losses.

In contrast thereto the inner connecting bend 13 between the inward fiowpassage and the outward flow passage is much more sensitive as regardsits formation for preventing flow separation along its inner radius. Forthis reason the inner bend 13 is formed in accordance with the inventionwith a nozzle-like restriction of at least 5%, the maximum restrictionbeing located at a section AA extending radially of the boundary surfaces and through the edge of the core ring 5 where the peripheralguidance at the inner radius of the recess 5a terminates. The startingplace of the restriction may vary within the range of two thirds of thelength of flow between the entrance and exit of the bend 13.

In the embodiment shown in FIG. 1 the starting place of the restrictionis such that the length of the restricted portion is the minimum lengthaccording to the invention, the cross-sectional area of the bend 13being substantially constant along two thirds of the length of the bend,and the succeeding gradual restriction is obtained by a suitable form ofthe hub of the impeller wheel 2.

If the inward flow passage 11 is not by more than 5% greater than theoutward flow passage 10 the area of the maximum restriction is less thanthe area at the impeller entrance. In order to prevent flow separationat the impeller entrance, a shoulder-like widening 2b of thecrosssectional area is formed in the hub of the propeller 2. The abruptwidening 2b causes separation at the outer boundary and a Carnot shockwith a resultant moderate vortex which reestablishes a thin boundarylayer at the layer at the impeller entrance.

Such a widening 2b is not confined to the above indicated area ratio ofthe inward to the outward flow passage, but can advantageously beapplied even in case of greater percentage differences between thecross-sectional areas of the inward and outward flow passages.

Along the inner radius flow separating at the impeller entrance iscounteracted due to the fact that a sealing slot between the innerradial edge of the inner ring 2c of the impeller and an internalprojecting surface of the core ring 5 is devised such that the leakingcurrent can be used to produce a Coanda effect or boundary layerreduction. This may be effected for instance :by forming the internalsurface of the core ring 5 with an angular projection 5b which togetherwith the inner ring 20 of the impeller defines a desired sealing slot byforming the curvature of the inner side of the inner ring 2c that facesthe impeller blades such as to cause the leaking current to flowradially outward along the ring 20. The leaking current has a highvelocity and therefore assists in making the boundary layer thinner andin counteracting flow separation along the inner side of the impellerblades 2a.

The formation of a hydraulic working chamber according to the inventionas applied to a torque converter of the two-phase type is shown in FIG.2 in which the gradually restricted portion of the inner bend 13 of thecircuit is of maximum length within the scope of the invention. Here thecross-sectional area of the inward flow passage 11 is by less than 8%greater than that of the outward flow passage, and even in this case ashoulderlike widening 2b of the flow passage is formed in the hub of theimpeller wheel 2 immediately ahead of the impeller entrance.

Similarly to the single-stage converter according to FIG. 1 the impellerblades 2a and the turbine blades 3a are located in the outward flowpassage 10 of the circuit and mechanical energy is similarly transmittedby the impeller 2 and taken out via the turbine wheel 3. The bearingsfor the impeller and the turbine and the location of their inner rings20, 30 relative to the external surface of the central core ring 5 arethe same as in the single-stage converter. In contrast thereto theinternal surface of the stationary casing 1a, 1b ofthe working chamberforms only the outer boundary of the outer bend 12 of the workingchamber. In the two-phase converter according to FIG. 2 the outerboundary of the inward flow passage 11 and the first quadrant of theinner :bend 13 in the direction of flow are formed by the hubs of tworeactor wheels 24, 25.

Thereactor wheel 24 is stationarily mounted in the casing 1a, 1b andcarries a set of fixed reactor blades 24a located substantially at thesame radius as the impeller blades 2a. Similarly to the previousembodiment the reactor blades 24a are connected to and support the corering 5.

The reactor wheel 25, the blades 25a of which are located radiallyoutside the reactor blades 24a is mounted for rotation via a free wheel14 as previously known in two-phase converters. The free wheel preventsrelative rotation of the reactor wheel 25 counter to the impeller wheel2 and turbine wheel 3, for instance during the start. At higher speedratios the reactor blades 25a are subjected to forces opposite to theforces acting during the start resulting in that the reactor wheel 25will be entrained and rotate freely in the liquid current withoutproducing reaction. It is therefore especially import-ant to reduce theflow losses in the reactor 25a by suitable design of these reactorblades as to curvature as well as thickness.

In the embodiment illustrated an inner ring 250 which interconnects thereactor blades 25a of the upper reactor fits a recess in the fixed corering 5 and merges smoothly into the outer boundary surface of the core.

The engagement and disengagement of the upper reactor blades 25a as anindirect function of the speed ratio of the engine and the adaptation ofthe torque converter to alternative gear ratios in combination with adifierential gear or the like form no part of the invention and are notdescribed in this connection.

The blade system used in two-phase converters can advantageously also beused in torque converters of the counter rotation type. As shown in FIG.3 the upper reactor blades 16a are in this case secured to one half a ofa two-part fcasing which encloses the working chamber. One end wall 15aof the casing is mounted for rotation in a central journal bearing 28and the other end wall 15b is rigidly connected to a ring gear 17 of aplanetary gearing. The planet gears 18 are rotatably mounted on shafts19 which are secured to a stationary casing 20 surrounding the torqueconverter. The sun gear 21 of the planetary gearing is movably mountedon the output shaft 3d of the turbine wheel and cooperates with saidshaft via a free-wheeling unit 22.

During backward rotation of the upper reactor blades 16a under reactionof the flow of fluid a corresponding torque is produced which via thecasing 15a, 15b is transmitted to the planetary gearing which reversesthe direction of the torque and via the free-Wheel 22 transmits thetorque to the output shaft 3d of the transmission. In this way thetorque of the upper reactor blades 16 is added to the output torque ofthe turbine Wheel resulting in a considerable torque multiplication. Thedescribed counter rotation torque converter is distinguished 'by a highstall torque and by a high efiiciency at high speed ratios.

In counter rotation torque converters it is possible to displace theefiiciency curve by transmitting the torque of the upper reactor blades16 to the sun gear 21 of the planetary gear in which case thecooperating torques are taken out at the ring gear 17. Such modificationneed not be described in this connection.

The cross-sectional area of the circuit of the embodiment shown in FIG.3 is defined in the outer part of the circuit in the same manner as inthe two-phase converter, whereas the inner boundary surface of thecircuit which may have a fixed core ring in accordance with FIG. 2consists of two parts in the counter rotation type illustrated. Thelower ring part 23 is secured to the stationary reactor blades 26a andthe upper part 27 is in the form of an inner connection ring for theupper reactor blades 16a.

In the embodiment illustrated in FIG. 3 the cross-sectional area at theimpeller entrance is only of the cross-sectional area at the reactorexit. For this reason the widening 2b of the cross-sectional areaimmediately ahead of the impeller blades 2a shown in FIGS. 1 and 2 isnot necessary in this embodiment. The cross-sectional area of the innerbend 13 is constant along two thirds of the length of flow between thereactor exit and the impeller entrance and is equal to thecross-sectional area at the reactor exit. After two thirds of the lengthof flow the hub of the impeller wheel 2 is formed such that thecross-sectional area will be gradually restricted to the maximumrestriction AA previously defined in this description. Thecross-sectional area at the place of maximum restriction is reduced tothe corresponding area at the impeller entrance, and the portion betweenthe maximum restriction at the impeller entrance is substantially ofconstant cross-sectional area.

What I claim is:

1. A hydrodynamic torque converter having a torusshaped working chamberfor a hydraulic working fluid, an impeller blade ring (2a) beingprovided in said chamber for rotation therein and being provided foreffecting a radial outward flow of the working fluid, at least oneturbine blade ring (3a) and at least one reactor blade ring (4a and 24a,16a, 26a, respectively) being provided in said chamber alternatively forradial outward flow and/ or for radial inward flow, said blade ringsforming radially inwardly and outwardly directed flow channels (10 and11) which are connected to an outer and an inner bladeless bend (12 and13, respectively) to form a closed transverse circuit of the workingchamber, said circuit having an outer boundary surface obtained by acombined cooperation between the internal surface of a casing (1a, 1band 15a, 1512, respectively) surrounding the working chamber and of thehubs of the blade rings, the inner boundary surface of said circuitbeing formed by the respective inner rings 2c, 30, 5 and 5, 25c and 23,27, respectively) of the blade rings, said inner rings being provided tofit into and to each other for forming of a central core in the workingchamber, characterized in that the through-flow area of the inner bend(13) of the circuit seen in the direction of flow is formed with asuccessively increasing restriction of at least 5% in order to obtainthe maximum restriction ahead of the impeller entrance in a section (AA)radial relative to the boundary surfaces of the impeller entrance andtaken through the edge of the core ring where the inner peripheralguidance for the inner ring (5 and 23, respectively) of the reactorblade ring terminates, and in that the starting place of the restrictionlies within a range of two-thirds of the length of flow between theentrance and exit of said bend (13), the through-flow area along thelength of flow between the entrance of the bend (13) and the startingplace of the restricted portion being preferably constant.

2. A torque converter according to claim 1, characterized in that asealing slot is provided between the radially inner edge of the impellerblade rin and the radially inner surface of a recess (5a) formed in theinner ring of the reactor blade ring, said sealing slot being so formedthat it will be possible to utilize the leaking current to obtain a socalled Coanda eifect, i.e. a reduction of the boundary layer so that theboundary layer along the inner sides of the impeller blades 2a) willbecome thinner and flow separation will be counteracted.

3. A torque converter according to claim 1, characterized in that theinternal surface of a recess (5a) in the inner ring of the reactor bladering is formed with a cam (5b) and in that the inner ring (20) of theimpeller blade ring is adapted to fit to said recess in such a way as togive a desired sealing slot, the radially inner edge of the inner ringagainst the impeller blades having a curvedshape which guides theleaking current to follow the ring (20) radially outwardly.

4. A torque converter according to claim 1, characterized in that incase the inward flow channel (11) has a through-flow area which is byless than 8% greater than the through-flow area of the impellerentrance, the through-flow area of the entrance downstream the maximumrestriction (A-A) seen in the flow direction and immediately ahead ofthe impeller entrance is formed 10 with a small shoulder-like widening(2b) which causes a Carnot shock with a moderate vortex whichreestablishes a thin boundary layer at the impeller entrance.

8 5. A torque converter according to claim 1, characterized in that theshoulder-like widening (2b) of the through-flow area is formed in thehub of the impeller (2).

References Cited UNITED STATES PATENTS 3,016,709 1/1962 Lyshom 60-543,071,928 1/1963 Dundore et a1. 60-54 3,105,396 10/1963 Dundore et a16064 XR EDGAR W. GEOGHEGAN, Primary Examiner.

